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非同期 스펙트럼 壙散 多重接續方式의 他局間 干涉除去에 관한 硏究
邊健植,金炫悳 동아대학교 공과대학 부설 한국자원개발연구소 1988 硏究報告 Vol.12 No.2
It is known that spread spectrum communication systems have a characteristics of nonsynchronous code division multiple access. Recently, SSMA(spread spectrum multiple access) is used in mobile communication and satellite communication. But the channel number of SSMA is limitted as SSMA have a poor cross-correlation between pn sequences in channels. This paper presents a new spread spectrum multiple access communication system without co-channel interference. SNR before and after the cancellation of co-channel interference is examinated. As a result of SNR, We confirmed that the efficiency of frequency usage is increased.
1次 및 2次 演算增幅器 時定數 效果에 무관한 스위치 케퍼시터 濾波器에 관한 硏究
邊健植 동아대학교 공과대학 부설 한국자원개발연구소 1982 硏究報告 Vol.6 No.1
Infinite gain amplifiers independent of first and second operational amplifier time constant effects using three operational amplifier is presented. Amplifier that is presented is comprised of bandpass filter. This filter is convert to switch capacitor filter using bi-linear transform. The active portion of this filter with presented amplifier is readily integrable since it is comprised of conventional operational amplifier and resistor. Experimental results show excellent agreement with theory.
SS 통신에서 적응 배열안테나와 ADF에 의한 간섭 제거
변건식,홍성일,정주수,이수영 동아대학교 공과대학 부설 한국자원개발연구소 1992 硏究報告 Vol.16 No.1
In realization of spread spectrum multiple access (SSMA), the reduction of interference signal of the same direction as the desired signals is very important in a practical communication. In order to solve this problem, this paper propose a modified adaptive array antenna including adaptive digital filter which reduce a interference of the same direction as the desired signals. As a result of simulation, we confirmed that the various demodulated error is reduced. Also, we confirmed that the proposed method accomplished a stable synchronization acquisition which had come influence of lock level.
PCM Voice CODEC의 Switched Capacitor Filter의 구성에 관한 연구
변건식,허강인 동아대학교 공과대학 부설 한국자원개발연구소 1984 硏究報告 Vol.8 No.2
Three Switched Capacitor decimation and interpolation circuits are described which perform all filtering functions in PCM Voice CODEC. The decimator can function as an input stage, the interpolator as an output stage in a filter system. The CODEC consists of 2 chips- the transmit chip includes the companding coder along with filtering functions, and the receive chip consists of the expanding decoder chip with its smoothing filter. Experimental results show the circuit to meet accepted requirements.
演算增幅器 時定數에 대한 O의 傳達函數感度를 갖는 能動 濾波器에 관한 硏究
邊健植 동아대학교 공과대학 부설 한국자원개발연구소 1982 硏究報告 Vol.6 No.1
Most second order RC active filters show a marked dependence on the gain-bandwidth product (GB) of operational amplifiers when the ω_(0) to be realized is greater than one percent of gain bandwidth product and Q is greater than 10. This paper presented that are independent of operational amplifier when ω_(0) is less than or equal 1 percent of gain bandwidth product and Q is less than or equal 10. Even for ω_(0)=0.05GB and Q=10, .the center frequency shift due to operational amplifier is less than 0.5 percent. This result is achieved by designing filter amplifiers which have zero sensitivity with respect to the time constants τ=1/GB of operational amplifier. As a result, the filter transfer function has also zero sensitivity with respect to τ.
최정식,이성신,김기표,변건식 東亞大學校附設 情報技術硏究所 2005 情報技術硏究所論文誌 Vol.13 No.1
OFDM technique which the available bandwidth is split into several narrowband subchannels at different frequencies is particularly suited for transmission over frequency selective channels. But if the states of some subchannel are bad, the performance of system become to decrease. The principle of bitloading is to adjust the date rate on the individual subchannels based on the current SNR. A subchannel with high SNR is then assigned more bits than a subchannels with lower SNR. As a results, we confirmed the superior performance if we used bitloading algorithm in OFDM system.
스펙트럼 擴散 多重接續(SSMA) 受信 方式의 채널간 干涉 除去에 관한 硏究
金明起,邊健植 동아대학교 공과대학 부설 한국자원개발연구소 1987 硏究報告 Vol.11 No.2
It is known that conventional spread spectrum communication systems have a characteristics of nonsynchronous multiple access. However, because the system has a mutual interference the number of channels that can communicate at the same time is small as compared with TDM. This paper presents a new spread spectrum multiple access communication system without mutual interference. The system was constructed and through experiment we confirmed that a improved amount of interference power when interference canceller be used increased to 24 ㏈ from 14 ㏈.
MIMO-PFDM 시스템에서 적응비트로딩 알고리즘의 성능평가
이민혁,변건석 동아대학교 정보기술연구소 2006 情報技術硏究所論文誌 Vol.14 No.1
Combined with multiple antennas at the transmitter and the receiver as well as adaptive modulation, OFDM proved to be robust against channel delay spread, in this paper. Futhermore, the optimal adaptive bitloading algorithm is proposed and the analysis was considered to involve the application of a variable-bit allocation and variable-power MQAM technique for a Single-Input Single-Output (SISO) OFDM system. This is compared with the performance of fixed OFDM transmission where a constant rate is applied to each subcarrier. The applied adaptive bitloading algorithm was in use as an inherent assumption in subchannel gain. Given this knowledge, the proposed system was designed to allocate the bit and power according to each subchannel. To prove the performance of adaptive bitloading algorithm, the simulation of SISO-OFDM system was conducted. It was concluded that the decision of bit numbers and power optimization algorithm served well to improve performance. Also, adaptive modulation was applied to a general MIMO system by making use of the singular value decomposition(SVD) to separate the MIMO channel into parallel subchannels. We can decompose the MIMO channel on each tone into parallel non-interfering SISO channels using the SVD. Namely, every matrix channel can be decomposed into a set of parallel subchannels over which data can be transmitted independently, given appropriate precoding and shaping transformations at the transmitter and the receiver, respectively. Finally, adaptive modulation combined with MIMO-OFDM system using an adaptive bitloading algorithm was applied to improve system performance. For a two-input antenna, two-output antenna system, the performance is compared with the performance of a system with a four-input antenna and a four-output antenna. Through MIMO-OFDM system simulation, we found that using more transmitter antenna and receiver antenna progress system performance because of increment of channel capacity, finally. Further, we concluded that the MIMO-OFDM system appling bitloading algorithm in general leads to better BER performance, as well as outperforming a common MIMO-OFDM system. A very useful extension of this paper would be in MIMO-OFDM systems with channel estimation technique. Throughout it, the performance analysis of more practical system is expected from now on.
BER을 경감하기 위한 직접파와 지연파를 분리, 합성하는 시스템
洪性一,邊健植,鄭宗宇,朴在云 東亞大學校 附設 情報通信硏究所 1993 情報通信硏究所論文誌 Vol.1 No.1
본 논문에서는 다중 경로에 따른 수신신호의 노화, 특히 이동통신에 대해서 문제가 되는 페이딩 대책으로 직접파와 지연파를 분리, 합성하는 적응 배열 안테나 시스템을 제시하고 분리된 직접파 출력 또는 지연파 출력만을 이용하는 시스템보다 두 신호를 합성한 시스템의 BER이 개선됨을 제시하였다. 시뮬레이션을 행한 결과 적응 배열 안테나가 적절히 동작하는 상황에 대해서는 분리된 출력을 적응적 Weight 조정을 하여 합성함으로써 직접파만을 이용하는 것보다 오율이 향상됨이 확인되었다.
寄生容量을 考濾한 스위치 케퍼시터濾波器의 設計에 관한 硏究
田龜濟,邊健植 동아대학교 공과대학 부설 한국자원개발연구소 1984 硏究報告 Vol.8 No.1
In this paper, the fundamental theory of switch capacitor filter is explained and the effect of parasitic capacitance is discussed in more detail. New equivalent circuits accounting for this parasitic effect are given. The relation between RC active filter and SC filter considering parasitic capacitances are presented by experiment. After all, it is concluded that error can be reduced significantly when we make these filters of MOS IC technology which has better temperature and linear characteristics.